Nuclear Theory·nucl-th

Friday·January 29, 2021

8 papers—5 primary·3 cross-listed

01
[Submitted on 28 Jan 2021]
Testing isospin symmetry breaking in ab initio nuclear theory
M. S. Martin🇨🇦 · S. R. Stroberg🇺🇸 · J. D. Holt🇨🇦 · K. G. Leach🇺🇸
In this work we present the first steps towards benchmarking isospin symmetry breaking in ab initio nuclear theory for calculations of superallowed Fermi $β$ -decay. Using the valence-space in-medium similarity renormalization group, we calculate b and c coefficients of the isobaric multiplet mass equation, starting from two different Hamiltonians constructed from chiral effective field theory. We compare results to experimental measurements for all T=1 isobaric analogue triplets of relevance to superallowed $β$ -decay for masses A=10 to A=74 and find an overall agreement within approximately 250 keV of experimental data for both b and c coefficients. A greater level of accuracy, however, is obtained by a phenomenological Skyrme interaction or a classical charged-sphere estimate. Finally, we show that evolution of the valence-space operator does not meaningfully improve the quality of the coefficients with respect to experimental data, which indicates that higher-order many-body effects are likely not responsible for the observed discrepancies.
Comments:
6 pages, 4 figures, 2 tables
Subjects:
Nuclear Theory (nucl-th); Nuclear Experiment (nucl-ex)
arXiv:
2101.11826 [pdf]
PRC(2021)·32 citations
02
[Submitted on 28 Jan 2021]
Simulating low-energy neutrino interactions with MARLEY
Steven Gardiner🇺🇸
Monte Carlo event generators are a critical tool for the interpretation of data obtained by neutrino experiments. Several modern event generators are available which are well-suited to the GeV energy scale used in studies of accelerator neutrinos. However, theoretical modeling differences make their immediate application to lower energies difficult. In this paper, I present a new event generator, MARLEY, which is designed to better address the simulation needs of the low-energy (tens of MeV and below) neutrino community. The code is written in C++14 with an optional interface to the popular ROOT data analysis framework. The current release of MARLEY (version 1.2.0) emphasizes simulations of the reaction $^{40}$ Ar $(ν_{e}, e^{-})^{40}$ K $^{*}$ but is extensible to other channels with suitable user input. This paper provides detailed documentation of MARLEY's implementation and usage, including guidance on how generated events may be analyzed and how MARLEY may be interfaced with external codes such as Geant4. Further information about MARLEY is available on the official website at http://www.marleygen.org.
Comments:
84 pages, 3 figures
Subjects:
Nuclear Theory (nucl-th); Computational Physics (physics.comp-ph)
arXiv:
2101.11867 [pdf]
Comput.Phys.Commun.(2021)·80 citations
03
[Submitted on 28 Jan 2021]
Low-density neutron matter and the unitary limit
Isaac Vidana🇮🇹
We review the properties of neutron matter in the low-density regime. In particular, we revise its ground state energy and the superfluid neutron pairing gap, and analyze their evolution from the weak to the strong coupling regime. The calculations of the energy and the pairing gap are performed, respectively, within the Brueckner--Hartree--Fock approach of nuclear matter and the BCS theory using the chiral nucleon-nucleon interaction of Entem and Machleidt at N $^{3}$ LO and the Argonne V18 phenomenological potential. Results for the energy are also shown for a simple Gaussian potential with a strength and range adjusted to reproduce the $^{1} S_{0}$ neutron-neutron scattering length and effective range. Our results are compared with those of quantum Monte Carlo calculations for neutron matter and cold atoms. The Tan contact parameter in neutron matter is also calculated finding a reasonable agreement with experimental data with ultra-cold atoms only at very low densities. We find that low-density neutron matter exhibits a behavior close to that of a Fermi gas at the unitary limit, although, this limit is actually never reached. We also review the properties (energy, effective mass and quasiparticle residue) of a spin-down neutron impurity immersed in a low-density free Fermi gas of spin-up neutrons already studied by the author in a recent work where it was shown that these properties are very close to those of an attractive Fermi polaron in the unitary limit.
Comments:
10 pages, 5 figures. Accepted for publication in Frontiers in Physics
Subjects:
Nuclear Theory (nucl-th); Quantum Gases (cond-mat.quant-gas)
arXiv:
2101.11903 [pdf]
Front.in Phys.(2021)·14 citations
04
[Submitted on 28 Jan 2021]
Nuclear binding energy predictions using neural networks: Application of the multilayer perceptron
Esra Yüksel🇹🇷 · Derya Soydaner🇹🇷 · Hüseyin Bahtiyar🇹🇷
In recent years, artificial neural networks and their applications for large data sets have became a crucial part of scientific research. In this work, we implement the Multilayer Perceptron (MLP), which is a class of feedforward artificial neural network (ANN), to predict ground-state binding energies of atomic nuclei. Two different MLP architectures with three and four hidden layers are used to study their effects on the predictions. To train the MLP architectures, two different inputs are used along with the latest atomic mass table and changes in binding energy predictions are also analyzed in terms of the changes in the input channel. It is seen that using appropriate MLP architectures and putting more physical information in the input channels, MLP can make fast and reliable predictions for binding energies of atomic nuclei, which is also comparable to the microscopic energy density functionals.
Comments:
20 pages, 5 figures
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.12117 [pdf]
IJMPE(2021)·20 citations
05
[Submitted on 28 Jan 2021]
A Semimicroscopic Algebraic Cluster Model for Heavy Nuclei
Peter O. Hess🇲🇽 · Leonardo J. Chavez-Nuñez🇲🇽
An extension of the Semimicroscopic Algebraic Cluster Model (SACM) is proposed, based on the pseudo-SU(3) model. The Hamiltonian and the spectroscopic factor operator of the model are presented and a procedure of constructing the model space. Because a huge number of SU(3) irreducible representations (irrep) appear, one has to be careful in designing a practical, consistent path to reduce the Hilbert space. The concept of forbiddenness, taking into account excitations of the clusters, is introduced and applied. The applications are to two systems with a low forbiddenness, namely to 236U -> 210Pb + 26Ne and 224Ra -> 210Pb + 14C, and to 236U -> 146Xe + 90Sr, which appears in the fission of 236U, which requires a large forbiddenness. Energies, electromagnetic transitions and spectroscopic factors are calculated.
Comments:
16 pages, 2 times 2 figures. arXiv admin note: text overlap with arXiv:1706.00067
Subjects:
Nuclear Theory (nucl-th)
arXiv:
2101.12133 [pdf]
EPJA(2021)·3 citations
06
[Submitted on 27 Jan 2021] (cross-list from hep-lat)
Towards studying the structural differences between the pion and its radial excitation
Xiang Gao🇺🇸 · Nikhil Karthik🇺🇸 · Swagato Mukherjee🇺🇸 · Peter Petreczky🇺🇸 · Sergey Syritsyn🇺🇸 · Yong Zhao🇺🇸
We present an exploratory lattice QCD investigation of the differences between the valence quark structure of pion and its radial excitation $π (1300)$ in a fixed finite volume using the leading-twist factorization approach. We present evidences that the first pion excitation in our lattice computation is a single particle state that is likely to be the finite volume realization of $π (1300)$ . An analysis with reasonable priors result in better estimates of the excited state PDF and the moments, wherein we find evidence that the radial excitation of pion correlates with an almost two-fold increase in the momentum fraction of valence quarks. This proof-of-principle work establishes the viability of future lattice computations incorporating larger operator basis that can resolve the structural changes accompanying hadronic excitation.
Comments:
11 pages, 7 figures; References added
Subjects:
High Energy Physics — Lattice (hep-lat); High Energy Physics — Experiment (hep-ex); High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.11632 [pdf]
PRD(2021)·16 citations
07
[Submitted on 28 Jan 2021] (cross-list from hep-ph)
CP-Symmetry in Scattering of Neutrinos from Nuclei
R.B. Begzhanov🇺🇿 · R.S. Sharafiddinov🇺🇿
The elastic scattering of longitudinal and transversal neutrinos on a spinless nucleus have been discussed taking into account the charge, magnetic, anapole and electric dipole moments of fermions and their weak neutral currents. Compound structure of the neutrino interaction cross section with nuclei have been defined. Invariance of the considered process concerning the C - and P-operations have been investigated in the polarization type dependence.
Comments:
7 pages, LaTex
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.11912 [pdf]
Bull.Russ.Acad.Sci.Phys.(2000)·0 citations
08
[Submitted on 28 Jan 2021] (cross-list from hep-ph)
New Developments in Relativistic Fluid Dynamics with spin
Samapan Bhadury🇮🇳 · Jitesh Bhatt🇮🇳 · Amaresh Jaiswal🇮🇳 · Avdhesh Kumar🇮🇳
In this work, we briefly review the progress made in the formulation of hydrodynamics with spin with emphasis on the application to the relativistic heavy-ion collisions. In particular, we discuss the formulation of hydrodynamics with spin for perfect-fluid and the first order viscous corrections with some discussion on the calculation of spin kinetic coefficients. Finally, we apply relativistic hydrodynamics with spin to the relativistic heavy-ion collisions to calculate the spin polarization of $Λ$ -particles.
Comments:
Minor text correction, few references added, 30 pages, 6 figures, Invited mini review
Subjects:
High Energy Physics — Phenomenology (hep-ph); Nuclear Theory (nucl-th)
arXiv:
2101.11964 [pdf]
Eur.Phys.J.ST(2021)·50 citations

Affiliations

first authorsco-authorsvia INSPIRE